Which institution should I use for automotive EMC testing?

Ask these four questions and most unsuitable labs drop out

First, does the scope of accreditation actually cover EMC? Many laboratories hold CMA / CNAS certificates whose scope lists environmental reliability or material analysis, with EMC nowhere in it. What you need is the item list in the annex to the scope, not the line of text on the certificate cover.

Second, is the anechoic chamber owned or rented, and are the main instruments your own? EMC is sensitive to the stability of the site and the instruments, and subcontracting brings uncertainty in both scheduling and quality. Ask whether the work is done in the lab's own chamber, and whether the report can be traced back to a specific site.

Third, which items can be covered? Automotive EMC splits into emissions and immunity, then further into radiated emissions, conducted emissions, radiated immunity, conducted immunity (including bulk current injection, BCI), electrostatic discharge and transient conducted immunity. A laboratory that runs emissions but not immunity cannot support a full OEM acceptance.

Fourth, capability in the test setup. CISPR 25 specifies harness length, load simulation, grounding method and antenna distance. If the setup is not right, the data cannot be compared with anyone else's, and the report cannot be aligned with your customer's historical data.

How automotive EMC differs from consumer-electronics EMC

• Stricter limits and wider frequency bands. Vehicle electronics have to coexist with the radio, communication modules and navigation, so emission limits are usually graded into classes specified by the OEM.
• A different supply environment. 12 V / 24 V systems require simulation of ignition, load dump and alternator ripple, so there are more test items than in consumer electronics.
• Different acceptance classes. Immunity tests are judged by functional status (A / B / C); for many products the requirement is not "must not fail" but "must recover by itself".
• Different reference standards. Automotive work refers to the CISPR 25, ISO 11452 and ISO 7637 series; consumer electronics to the CISPR 32 series. The two systems are not interchangeable.

Three common traps

Reading the certificate and not the scope. This is one of the most frequent misjudgements: the certificate is genuine, but the item falls outside the scope, so the report is unusable.

Submitting samples without defining their state. Operating mode, load conditions and harness length all shift the emission data noticeably. Agree on the test state before shipping samples and write it into the commissioning form.

Testing emissions but not immunity. OEM acceptance normally requires both sides; doing half means a supplementary run, and both time and cost double.

What to prepare before submitting samples

• A description of the operating modes and the typical loads
• The harness drawing and the actual vehicle harness length (CISPR 25 specifies the length)
• The reference standard and revision specified by the customer, plus the functional status class
• The OEM corporate standard, if any — it takes precedence over the generic standard

Where we stand

TMC LAB holds both CMA and CNAS accreditation, with a laboratory of roughly 10,000 m². All testing is performed in our own laboratory, with no subcontracting. Automotive EMC covers the CISPR 25 and ISO 11452 series, and the reports can be used for OEM validation and export certification. Site visits and witness testing are welcome.

To find out whether your specific project can be taken on, and which revision of the standard applies, send us the product model and the test requirements. Our engineers check the scope of accreditation first and then reply — we do not quote before confirming.